ultrasound today

had ultrasound today at 37+ weeks (gestational diabetic) and now they've got me all nervous. her heart rate is good, cord is where it should be, head is down but they couldn't see my cervix she's so low. she's measuring at 36 weeks though, and they called the doc to see if I needed to come in sooner then my next scheduled appointment. ultrasound techs can't tell you anything other then " things look good" what are they looking for? I'm nervous and don't know what to do. I'm sure I'm over thinking things but since the tech thought I needed to see the doc sooner I'm just on edge. I think I just need someone to tell me everything is fine and to stop worrying.